This application is directed, in its description and illustrations, toward cleaning waste (or foreign) material from work pieces after they have been machined. It is to be understood that the same cleaning processes and apparatus could be used to remove other types of unwanted material from other types of holes, in other types of work pieces.
As used herein, the term "hole" includes such structures as conventional holes that are drilled with metal drill bits. It includes "through holes" which extend through the work piece, between two surfaces of the work piece, and thus are open on both ends. (Such holes may or may not have been made with the likes of a metal drill bit.) It includes "blind holes" which extend, from the work piece surface, into the work piece, and terminate on the interior of the work piece. It further includes cavities which existed in the casting or the like prior to the machining operation, and which are so configured as to accommodate receiving and holding of waste material generated by the machining operation.
As used herein, the term "machining" refers to milling, drilling, tapping of holes, and the like. Especially tapping operations produce holes which are difficult to clean thoroughly.
The basic application of the problem addressed by this invention is that of cleaning machining shavings and like waste from machined work pieces after the machining operations have been completed. Typically, after a casting has been machined, some of the shavings and other waste from the machining operations are lodged and/or impacted in the holes in the casting.
Because machined work pieces are typically used in assembled equipment, such as an internal combustion engine, where parts move in close relationship with each other, any waste from the machining operations which gets between the moving parts in the assembly can severely damage the assembled equipment. Thus, it is critical to remove from the machined work pieces any machining waste which would interfere with the operation of the e.g. engine. Such interference might occur in the location occupied by the waste when the machining operation is completed; or might occur if the waste is later dislodged from the work piece, whereby the waste can move around in the engine during operation of the engine. No interference is suggested where the waste occupies a position where it will not interfere with the assembly or operation of the assembled equipment, and will not be dislodged during operation of the assembled equipment.
Machining waste from machining metal castings generally comprises metal shavings of various sizes, chips or dust, and the like.
A variety of methods have been tried for cleaning machining waste from machined castings. The casting is conventionally flushed with a cutting fluid during some machining operations. This flushing does accomplish some initial but incomplete cleaning.
It is also known to subject the castings to bursts of compressed air, as described in U.S. Pat. No. 5,071,487 to McKibben et al.
It is further known to wash the work piece by submerging it in a solvent and, while the work piece is so submerged, to direct streams of solvent at holes in work piece, to try to dislodge waste material from the holes. U.S. Pat. No. 4,867,186.
While such methods do remove some, and in some cases do remove most, of the waste from the work piece, it is critical that all interfering waste material be removed. Otherwise, the high potential value of the work piece is not obtained, because the presence of the interfering waste material makes the work piece defective. In order to ensure obtaining the high potential value of the work pieces, manufacturers must, accordingly, inspect a high fraction of the work pieces in order to assure that all interfering waste material is removed from all work pieces.
A 100% inspection of all machined work pieces, for detecting and removal of machining waste, is commonly employed in some industries. Such an operation is labor intensive, and thus costly. It would be desirable to have a dependable method of cleaning machining waste from machined work pieces, such that the commitment of resources to the inspection for, and removal of, machining waste could be reduced.
It is an object of this invention to provide a cleaning system that can reliably clean foreign material from holes in work pieces such as machined castings and the like.
It is a more specific object to provide a system having such capabilities, wherein nozzles blast pressurized gas, through an intervening liquid, into the holes which need to be cleaned in such work pieces.
A related object is to provide a cleaning system that has nozzles so arranged and configured that the system can be used to clean holes in a plurality of related but different work pieces, wherein the arrays of holes in the different work pieces do differ.
Another related object related to use of the cleaning system is to provide for leveling the demand on the compressor or other source of pressurized gas.
It is another object of the invention to provide methods of cleaning holes in work pieces, by expressing blasts of gas, through a liquid medium, and into the holes.
It is a more specific object to provide a method that incorporates using a plurality of cycles, wherein each cycle includes a short period of expressing a blast of pressurized gas into the hole, followed by a period of rest wherein no pressurized gas is directed at the hole.
It is yet another object to provide a method of cleaning through holes by blasting the through hole from both ends, in sequence, so that foreign material lodged therein is urged first in one direction, then in the opposite direction.